The invention relates generally to an improved pipe coupling assembly and, more particularly, to an easily assembled and disassembled pipe coupling assembly.
Known methods for connecting a length of metal pipe or tubing to valves or pipe fittings such as elbows and tees include the use of threaded connectors, soldering, compression fitting, flaring and welding. Non-metallic pipe, such as thermoplastic pipe, may also be joined by adhesives.
These methods are all subject to various drawbacks. Methods calling for the application of heat or force can be awkward and time consuming to practice in cramped and inaccessible areas, for example, areas in which residential plumbing is typically located. Soldering, welding and the like require the attention of a skilled worker using special tools to produce a good connection. Moreover, it is often difficult and time consuming to disconnect a length of pipe from a fitting once they have been joined, and it is often not possible to disassemble the joint without damaging the pipe or the fitting to such an extent that they cannot later be rejoined.
Acceptable pipe joints are more difficult to make when the pipe is to carry a fluid under pressure. Even where threaded pipe and threaded connectors are used, greater skill is required to produce a strong and leakproof seal which will withstand the pressure rating of the pipe being joined. For proper sealing under pressure, washers or O-rings are often included in the joint. If the washer and pipe are made of dissimilar metals, they will sometimes undergo electrolysis in the presence of moisture in the joint or water and chemical agents flowing through the pipe. Electrolytic action leads to degradation of the washer, which can eventually cause the joint to leak and loosen the locking action of lock washers.
Some of the aforementioned drawbacks are overcome by the use of plastic pipe joined by adhesive. But plastic pipe is difficult to connect directly to metal valve fittings without special adaptors. Moreover, once sealed with adhesive, prior plastic pipe joints cannot be readily undone. Disclosed in U.S. patent application Ser. No. 07/944,373, now U.S. Pat. No. 5,328,215, is an improved coupling assembly that is illustrated in FIGS. 1-9. A pipe coupling assembly 11 includes an inner first tubular member 12 and an outer receiving tubular member 13. The tubular member 12 generally will be a length of pipe or tubing such as commonly employed for the delivery of fluids. The embracing tubular member 13 will generally form a part of a pipe fitting, such as an elbow, tee, or the like, or will form a part of some other component of a piping system, such as a valve.
The receiving tubular member 13 includes an inner portion 14, an outer portion 15 and an end portion 16 with a radially inwardly directed rim 18 that defines a circular opening 17 and an inwardly directed shoulder 19. Defined by the inner portion 14 of the receiving tubular member 13 is an inner bore 21 dimensioned to snugly receive the outer surface of the first tubular member 12. The outer portion 15 of the receiving tubular member 13 defines an annular cavity 22 intercepting the inner bore 21 and projecting radially outwardly therefrom. Forming the annular cavity 22 is a cylindrical wall portion 24 and an annular tapered wall portion 25 joining the cylindrical wall portion 24 and the shoulder 19 surrounding the opening 17. An annular gap 27 is formed between the first tubular member 12 and the rim 17 which has a diameter larger than the outer surface thereof. Defining an annular shoulder 28 on the receiving tubular member 13 is a counterbore 29. An annular rib 31 on the receiving tubular member 13 projects inwardly from the cylindrical portion 24 and separates the cavity 22 into longitudinally separated cavity portions 32 and 33. Projecting inwardly from the cylindrical wall portion 24 in the cavity portion 32 is a longitudinally disposed ridge 34.
The pipe coupling assembly 11 also includes a split lock ring 35 disposed in the cavity portion 32, a sealing member 36 such as a resilient O-ring disposed in the cavity portion 33, and a split auxiliary ring 37 disposed in the cavity portion between the lock ring 35 and the annular rib 31.
The lock ring 35 is made from a material suitable to establish a good spring characteristic. As shown in FIGS. 3-5, the lock ring 35 has a circular cross-section, an outer circumferential surface portion 41 of diameter D less than the diameter of the adjacent cylindrical wall portion 24, and an inner circumferential surface portion 42 of diameter d less than the outer diameter of the first tubular member 12. Cut in the inner surface portion 42 is a circumferential groove 44 formed by one wall 43 oriented perpendicular to an outer surface 45 of the first tubular member 12, and another wall 47 extending between the outer surface of the ring 35 and the one wall 43 and oriented perpendicular thereto. The another wall 47 extends from the one wall 44 toward the opening 17 in the tubular member 13. Formed by the periphery of the one wall 43 is a circumferential knife edge 48 extending parallel to the outer surface 45 of the first tubular member 12. First and second ends 51, 52 of the lock ring 35 straddle a split therein and, as shown in FIG. 3, the second end 52 is axially displaced from the first end 51 which is circumferentially aligned with the major portion of the ring 35.
During assembly of the coupling 11, the first tubular member 12 is inserted through the opening 17 in the receiving tubular member 13 until an inner end 68 of the member 12 engages the annular shoulder 28 as shown in FIG. 4. As the first tubular member 12 moves through the annular cavity 22, its external surface engages the knife edge inner surface 48 of the lock ring 35 expanding it outwardly into the cavity portion 32 of the annular cavity 22. However, since the outer diameter D of the lock ring 35 is less than that of the cylindrical wall portion 24, inward axial movement of the first tubular member 12 is not restricted. In addition, the auxiliary ring 37 is compressed between the cylindrical surface portion 24 and the outer surface of the first tubular member 12 which outer surface is scored by the longitudinal projecting edges 64. Because of this penetration of the first tubular member 12 by the edges 64 on the compressed auxiliary ring 37, rotation of the first member 12 within the receiving member 13 is prevented. A tapered annular transitional surface 69 between the cylindrical surface portion 24 and the inner bore 21 accommodates longitudinal migration of the sealing member 36 so as to prevent damage thereto during insertion of the first tubular member 12 as shown in FIG. 8.
After full insertion, the first tubular member 12 is partially withdrawn to produce a longitudinal separation movement relative to the receiving tubular member 13. During that movement, the lock ring 35 is forced longitudinally outwardly in the annular cavity 22 and tightly compressed therein between the shoulder stop 19, the tapered wall portion 25 and the outer surface of the first tubular member 12 as shown in FIG. 9. Because of the penetration of the outer surface of the first tubular member 12 by the knife edge 48 on the lock ring 35, further relative longitudinal movement between the member 12 and the receiving tubular member 13 is prevented. In addition, the second end 52 of the lock ring 35 is forced into circumferential alignment with the first end 51 creating an axially directed force that biases the member 12 inwardly in the member 13. Fluid pressure within the coupling 11 exerts on the first member 12 a longitudinally outwardly directed force F that is transferred by the tapered wall portion 25 radially inwardly on the lock ring 35. Consequently, the knife edge 48 is driven further into the outer surface of the first member 12 and enhancing the securement thereof to the receiving member 13. With the parts in the relative positions shown in FIG. 9, the O-ring 36 is engaged between the cylindrical surface portion 24 and the outer surface of the first tubular member 12 to create a fluid tight seal therebetween. The annular rib 31 prevents damage of the annular sealing member 36 by the teeth 63 on the auxiliary ring 37.
The coupling assembly 11 alleviates many of the above noted problems. However, the operational characteristics of the coupling 11 are not suitable for all applications.
The object of this invention, therefore, is to provide an improved high pressure pipe coupling assembly that can be easily assembled and disassembled by unskilled workers.